1. Field of the Invention
This invention relates to a process for the production of phenol esters which, in recent years, have acquired interest as activators for inorganic peroxy compounds, particularly where they are used as bleaching agents.
2. Statement of Related Art
Acyloxybenzene sulfonates can be produced from the phenol sulfonates by reaction with the corresponding anhydrides either in the absence of solvents or in suitable solvents. However, the higher anhydrides are relatively expensive and the reaction mixture is difficult to work up. Accordingly, the reaction of phenol sulfonates with the corresponding acid chlorides is more common. European patent application 120 591 describes this reaction in anhydrous organic solvents, such as chlorobenzene. However, difficulties are involved in removal of the HCl released or NaCl (after addition of base). Where excess acid chloride is used as the solvent, as proposed in European patent application 148 148, removal of the end product in pure form involves certain problems. In addition, it is necessary in all these proposals to use strictly anhydrous reagents and solvents and to carry out the acylation reaction in the absence of moisture. An alternative reaction with, basically, more favorable prospects is the Schotten-Baumann acylation proposed for these compounds in European patent application 294 073. In the Schotten-Baumann acylation, base, phenol sulfonate and a small quantity of a surfactant are dissolved in water and benzoyl chloride is subsequently added dropwise to the resulting solution. However, the acylation reaction has to be carried out in a relatively narrow temperature range and separation of the end product in high yields is only possible if the reaction is subsequently cooled to temperatures in the range from about 0.degree. to 5.degree. C. To avoid contamination by relatively large quantities of the corresponding carboxylic acid, surfactant has to be added. Working up on an industrial scale is complicated above all by the need to cool the reaction mixture as a whole to isolate the end product and to wash the end product, even at low temperatures, and also by addition of the surfactant.